Is there a benefit of reduced-intensity conditioning plus imatinib compared to imatinib alone?

This study examined two types of treatment regimes involving imatinib (Gleevac) for chronic myeloid leukemia (CML). Patients receiving reduced-intensity chemotherapy and a stem cell transplant before imatinib had similar outcomes to patients treated with imatinib alone.

Targeted therapy has become the standard first-line treatment for CML. Targeted therapy is a type of treatment that uses drugs or small molecules that block the growth and spread of cancer. Tyrosine kinase inhibitors, such as imatinib, are a type of targeted therapy that block enzymes called tyrosine kinases.

In the chronic phase, CML progresses slowly. Since imatinib does not have many side effects, it can be safely administered as a long-term treatment. However, imatinib is not considered a cure for CML. Continued therapy is needed in order to maintain a clinical response.

It has been suggested that fit patients may benefit from reduced-intensity chemotherapy followed by a stem cell transplant from a donor. This is also known as reduced intensity hematopoietic stem cell transplantation (or RIST). RIST is designed to suppress the patient's immune system enough so that it will accept the donor stem cells. Once the donor's cells take over the patient's bone marrow (a process known as engraftment), the immune system is better able to kill cancer cells.

The aim of this study was to compare the outcomes of RIST plus imatinib versus imatinib alone.

42 patients were treated with RIST plus imatinib. 88 patients were treated with imatinib alone. The average age at treatment was 34 years. 102 patients were in the early chronic phase (had CML for less than 12 months). 28 patients were in the late chronic phase (had CML for 12 months or more). Patients were followed for an average of 57 months.

The 10-year overall survival rate (proportion who have not died from any cause since treatment) was comparable between the two groups. It was 85.5% for RIST plus imatinib and 89.1% for patients treated with imatinib alone. The risk of a treatment-related event such as progression or death was also similar between the groups.

Late chronic phase, high-risk disease, and poor treatment response at 3 months were each associated with poorer survival outcomes.

Further analysis showed that among patients in the late chronic phase, more patients in the imatinib group experienced an event such as progression or death. 40.8% of late-phase patients treated with imatinib alone were event-free at 10 years. This was significantly lower compared to those treated with RIST plus imatinib (66.7%).

Patients with higher Bone Marrow Transplant scores (a standardized risk score calculated before a stem cell transplant) had poorer survival. Overall survival was significantly lower for those with a high score (69.2%) compared to those with a low score (92.9%).

Researchers reported similar outcomes for RIST plus imatinib versus imatinib alone. However, RIST plus imatinib may be a suitable treatment options for patients with lower risk.

Larger studies that randomly assign patients to treatment groups are needed to confirm these results.